<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
    <script>
        var score = prompt('请输入成绩');
        switch(true){
            case score>=90:
                alert('优秀');
                break;
            case score<90&&score>=80:
                alert('良好');
                break;
            case score<80&&score>=70:
                alert('及格');
                break;
            default:
                alert('不及格');
                break;
        }



    </script>
</body>
</html>